JP2009047833A - Image forming device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of forming an image with satisfactory image quality, even on a continuous paper sheet with a partially fluctuated resistance value. <P>SOLUTION: This image forming device has transfer rollers 24Y, 24M, 24C, 24K for transferring toner images formed on image carriers 22Y, 22M, 22C, 22K onto the continuous paper sheet, a voltage measuring part 102 for supplying currents to the transfer rollers 24Y, 24M, 24C, 24K, and for measuring continuously voltages of the transfer rollers 24Y, 24M, 24C, 24K when the transfer rollers 24Y, 24M, 24C, 24K contact with the continuous paper sheet, and a control part 100 for setting current values supplied to the transfer rollers 24Y, 24M, 24C, 24K when transferring the toner images onto the continuous paper sheet, and current value changing timings, in response to the measured voltages. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image on continuous paper at high speed.

Conventionally, a corona transfer type transfer device has been generally used as a transfer device of an image forming apparatus that forms an image on continuous paper at a high speed. However, the use of a transfer roll method is desired because poor transfer occurs due to the use of poor paper or thin paper, or paper wrinkling during multi-continuous printing.
The transfer roll method is a technique that is generally used in cut paper printers. As a charge application method to the transfer roll, a constant current control method that controls the current value flowing through the transfer roll to be constant is generally used. It has been adopted.

  Patent Document 1 discloses that when transferring toner to an area of continuous paper affected by the heat of a fixing unit that heats and fixes toner transferred onto continuous paper, the transfer current of the transfer unit is set higher than usual. is doing.

  In Patent Document 2, when a conductive label is printed as a print target label, the transfer current in a predetermined section from the start of charging of the print target label is made larger than the transfer current in other sections.

JP 2005-24577 A Japanese Patent Laid-Open No. 7-302001

  However, if a card medium or the like is embedded in the continuous paper, the resistance value differs greatly between the plain paper portion and the card medium portion. When the above-described constant current control is performed on such continuous paper, there is a problem that good transferability cannot be obtained.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image forming apparatus and method capable of forming an image with good image quality even with a transfer material whose resistance value varies partially. And

In order to achieve the above object, an image forming apparatus according to the present invention includes a transfer roll that transfers a toner image formed on an image carrier to a transfer material, supplies current to the transfer roll, and the transfer roll uses the transfer material. Measuring means for continuously measuring the voltage of the transfer roll when in contact with the toner, measuring a current value supplied to the transfer roll when the toner image is transferred to the transfer material, and a timing for changing the current value And setting means for setting based on the applied voltage.
As described above, according to the present invention, by providing a measuring means for measuring a change in the voltage of the transfer roll by supplying an electric current to the transfer roll, even with a transfer material in which the resistance value partially fluctuates, the image quality is excellent. An image can be formed.

  In the image forming apparatus, the measuring unit may measure the voltage of the transfer roll by conveying the transfer material to a conveyance path before forming an image.

  The image forming method of the present invention includes a step of supplying a current to a transfer roll, continuously measuring a voltage of the transfer roll when the transfer roll is in contact with the transfer material, and a toner image to the transfer material. And setting a current value supplied to the transfer roll during transfer and a change timing of the current value based on the measured voltage.

  According to the present invention, it is possible to form an image with good image quality even on a sheet whose resistance value varies partially.

  Preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  First, the configuration of the present embodiment will be described with reference to FIG. As shown in FIG. 1, the image forming apparatus 1 according to the present embodiment prints each of the color toner images of yellow (Y), magenta (M), cyan (C), and black (K) sequentially onto continuous paper P. A printing unit 12Y, a printing unit 12M, a printing unit 12C, and a printing unit 12K. The printing unit 12Y, the printing unit 12M, the printing unit 12C, and the printing unit 12K are arranged in order from the upstream side in the conveyance direction of the continuous paper P to the downstream side. On the upstream side in the conveyance direction of the printing unit 12Y, a paper conveyance unit 14 that conveys the continuous paper P fed from the unwinding roll 70 to each of the printing unit 12Y, the printing unit 12M, the printing unit 12C, and the printing unit 12K is provided. Yes. A fixing unit 16 and a fixing unit 16 for fixing the color toner images transferred by the printing unit 12Y, the printing unit 12M, the printing unit 12C, and the printing unit 12K to the continuous paper P are provided downstream of the printing unit 12K in the conveyance direction. A paper discharge unit 17 that discharges the continuous paper P that has passed is provided.

  The paper transport unit 14 includes a transport roller 18 around which the continuous paper P is wound. An idle roll 19 </ b> D is pressed against the transport roller 18. The continuous paper P is nipped and conveyed by the nip portion between the idle roll 19D and the conveyance roller 18, and is conveyed to the printing unit 12Y via the idle roll 19C.

  The print unit 12Y, the print unit 12M, the print unit 12C, and the print unit 12K include an image carrier 22Y, an image carrier 22M, an image carrier 22C, and an image carrier 22K. The image carrier 22Y, the image carrier 22M, the image carrier 22C, and the image carrier 22K are detachably held by the holding member 23Y, the holding member 23M, the holding member 23C, and the holding member 23K, and the continuous paper P Are arranged along the transport path.

  The printing unit 12Y further includes a transfer roller 24Y, a guide roll 40Y, a cleaning device 28Y, a charging charger 30Y, an LED head 32Y, and a developing device 34Y. The charging charger 30Y uniformly charges the image carrier 22Y. For example, the charging charger 30Y applies a negative voltage obtained by superimposing a negative DC bias voltage on an AC voltage. The LED head 32Y forms an electrostatic latent image on the image carrier 22Y by exposing the image carrier 22Y uniformly charged by the charger 30Y based on the image data corresponding to the Y color. The developing device 34Y is provided on the downstream side in the image carrier rotation direction B of the LED head 32Y, and forms a Y-color toner image corresponding to the electrostatic latent image formed on the image carrier 22Y. A negative developing bias voltage obtained by superimposing a negative DC bias voltage on an AC voltage is applied to the developing device 34Y. By the developing device 34Y adsorbing the Y color toner only on the electrostatic latent image forming area of the image carrier 22Y, a toner image composed of negatively charged Y toner particles corresponding to the electrostatic latent image is formed. It is formed on the image carrier 22Y.

  The Y toner image formed on the image carrier 22Y by the developing device 34Y is applied with a transfer bias described in detail later by the transfer roller 24Y, so that a toner image composed of negatively charged toner particles is formed. The toner 22 is drawn toward the continuous paper P from the carrier 22Y, and the toner image is transferred onto the continuous paper P. The cleaning device 28Y scrapes off and removes untransferred residual toner remaining on the surface of the image carrier 22Y without being transferred to the continuous paper P.

  Similar to the printing unit 12Y, the printing unit 12M further includes an image carrier 22M, a transfer roller 24M, a guide roll 40M, a cleaning device 28M, a charging charger 30M, an LED head 32M, and a developing device 34M. Similarly to the printing unit 12Y, the printing unit 12C further includes an image carrier 22C, a transfer roller 24C, a guide roll 40C, a cleaning device 28C, a charging charger 30C, an LED head 32C, and a developing device 34C. Further, like the printing unit 12Y, the printing unit 12K further includes an image carrier 22K, a transfer roller 24K, a guide roll 40K, a cleaning device 28K, a charging charger 30K, an LED head 32K, and a developing device 34K. Each configuration of the printing unit 12M, the printing unit 12C, and the printing unit 12K has the same function as the above-described printing unit 12Y, and thus detailed description thereof is omitted.

  The fixing unit 16 includes a flash fixing device 52, an idle roll 54A, an idle roll 54B, an idle roll 54C, and a paper discharge roll 56. The idle roll 54A, idle roll 54B, and idle roll 54C convey the continuous paper P wound around these idle rolls upside down. The flash fixing device 52 irradiates the toner image forming surface of the continuous paper P with infrared rays. After the unfixed toner on the continuous paper P is heated and melted by infrared irradiation, the toner images are fixed on the continuous paper P by solidifying. The continuous paper P that has passed through the flash fixing device 52 is transported to the paper discharge unit 17, transported again to the fixing unit 16 via the idle roll 59 </ b> A and idle roll 59 </ b> C, and then discharged to the outside of the device by the paper discharge roll 56. Then, the film is wound on a winding roll 80.

FIG. 2 shows a configuration of the transfer roll 24 and an apparatus that controls the current applied to the transfer roll 24. This apparatus includes a current output unit 101, a voltage measurement unit 102, and a control unit 100. Hereinafter, when there is no need to distinguish between the respective colors such as the transfer rolls 24Y, 24M, 24C, and 24K and the charging chargers 30Y, 30M, 30C, and 30K, they are represented as the transfer roll 24 and the charging charger 30 as representatives. To do.
The current output unit 101 supplies current to the transfer roll 24 under the control of the control unit 100.
The voltage measuring unit 102 measures the voltage generated in the transfer roll 24 by supplying current to the transfer roll 24. The measured voltage value is notified to the control unit 100.
The control unit 100 controls the current value that the current output unit 101 supplies to the transfer roll 24 based on the measurement voltage of the voltage measurement unit 102.

In this embodiment, as shown in FIG. 3, the card medium 110 is printed on a part of the continuous paper at a predetermined interval, and an image is formed on the continuous paper having a partly different resistance value.
In order to form an image with good image quality on such a continuous paper whose resistance value fluctuates, the control unit 100 uses the current output unit 101 and the voltage measurement unit 102 to detect the fluctuation period of the resistance value of the continuous paper. Yes. By measuring the voltage fluctuation of the transfer roll 24 when a constant current is applied to the transfer roll 24, the fluctuation of the resistance value of the continuous paper can be detected. FIG. 4 shows a change in voltage measured by the voltage measuring unit 102 when continuous paper is flowed through the paper conveyance path of the image forming apparatus 1 at a constant speed and a constant current is applied to the transfer roll 24. When the plain paper portion 120 having a low resistance value is in contact with the transfer roll 24, the voltage measured by the voltage measuring unit 102 is also reduced as shown in FIG. 4, but when the card medium 110 having a high resistance value is in contact with the transfer roll, As shown in FIG. 4, the voltage measured by the voltage measurement unit 102 also increases.

The control unit 100 determines the current supplied to the transfer roll 24 when the plain paper portion 120 of the continuous paper is in contact with the transfer roll 24 based on the voltage fluctuation measured by the voltage measurement unit 102 and the sheet conveyance speed, and the card medium. A current supplied to the transfer roll 24 when the portion 110 contacts the transfer roll 24 and a change timing for switching the current value are set.
Note that the step of supplying a current to the transfer roll 24 and measuring the voltage of the transfer roll 24 is performed at the time of non-printing paper passing such as alignment correction and paper discharge or at the time of auto-loading.
The alignment correction is to set the image formation start position on the continuous paper. When an image is formed on continuous paper, the speed at which the continuous paper is unwound from the unwinding roll 70 and conveyed to the image forming position varies. Alignment processing for setting the formation position is performed.
The autoload is a function that automatically feeds the leading edge of the continuous paper to the conveying path when printing of the next continuous paper is completed after the printing of the continuous paper is completed, and connects the continuous paper after printing.

FIG. 5 shows changes in transfer efficiency (%) when the current (transfer current) applied to the transfer roll 24 is changed. In order to obtain a good image quality with a transfer efficiency of 90% or more, a current of 200 μA to 400 μA is required for the plain paper portion 120 and a current of 300 μA to 550 μA is required for the card medium portion 110. However, in actuality, since it is necessary to keep the current flowing into the image carrier 22 low in the plain paper portion, 200 μA to 250 μA is selected as the transfer current. For the same reason, when the card medium 110 is in contact with the transfer roll 24, a transfer current of 300 to 350 μA is selected.
As described above, the optimum transfer current value supplied at the time of transfer differs between the plain paper portion and the card medium portion of the continuous paper.
Therefore, the control unit 100 performs control to change the current value supplied to the transfer roll 24 when the plain paper comes into contact with the transfer roll 24 and when the card medium comes into contact.

The processing procedure of this embodiment will be described with reference to the flowchart shown in FIG.
When the conveyance of the continuous paper is started (step S1), the control unit 100 brings the transfer roll 24 into contact with the image carrier 22 (step S2). Then, the current output unit 101 is controlled to supply a constant current to the transfer roll 24 (step S3). At this time, the control unit 100 continuously measures the voltage of the transfer roll 24 by the voltage measurement unit 102.
When the voltage measurement is completed, the control unit 100 sets the cycle of the current supplied to the transfer roll 24 based on the measured voltage fluctuation and the sheet conveyance speed (step S4).

As described above, the present embodiment can form a good image even on a continuous paper having areas with partially different resistance values, such as a card medium printed on plain paper.
In the above-described embodiment, the continuous paper is flowed through the conveyance path to supply a current to the transfer roll, and the voltage is measured to detect the change in the resistance value, but according to the user's operation input from the operation unit, The current supplied to the transfer roll may be changed.

The embodiment described above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.

1 is a diagram illustrating a configuration of an image forming apparatus. It is a figure which shows the structure of the apparatus which controls the transfer roll and the electric current applied to a transfer roll. It is a figure for demonstrating the continuous paper used for printing. It is a figure which shows the voltage applied to a transfer roll in a plain paper part and a card | curd medium part. It is a figure which shows the relationship between the transfer current (microampere) and transfer efficiency (%) in a plain paper part and a card | curd medium part. It is a flowchart which shows the process sequence of a control part.

Explanation of symbols

1 Image forming apparatus 22Y, 22M, 22C, 22K Image carrier 23Y, 23M, 23C, 23K Holding member 24Y, 24M, 24C, 24K Transfer roll 32Y, 32M, 32C, 32K LED head 34Y, 34M, 34C, 34K Developing device 100 Control Unit 101 Current Output Unit 102 Voltage Measurement Unit

Claims (3)

A transfer roll for transferring the toner image formed on the image carrier to a transfer material;
Measuring means for supplying a current to the transfer roll and continuously measuring the voltage of the transfer roll when the transfer roll is in contact with the transfer material;
Setting means for setting a current value to be supplied to the transfer roll when the toner image is transferred to the transfer material, and a change timing of the current value based on the measured voltage;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the measuring unit transports the transfer material to a transport path before forming an image and measures the voltage of the transfer roll. Supplying a current to the transfer roll, and continuously measuring the voltage of the transfer roll when the transfer roll is in contact with the transfer material;
Setting a current value supplied to the transfer roll during transfer of the toner image to the transfer material, and a change timing of the current value based on the measured voltage;
An image forming method comprising:

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